Unless it has Contrary, Leaf Storm is nothing to wait for. I usually evolve my pokemon (they'll learn the move sooner or later) and because who wants a weaker base form pokemon, yeah they're cute...but come on.

I have decided that some of my pokemon are not going to evolve as soon as they can, and some i don't even want to evolve at all. Though sooner or later the majority will evolve into their final form, but not for a while. I think I'll let my snivy chill as snivy for a while, and the same with my darumakka. My marril will probably stay a marril though, conversely i really would like to have my sandile become krookodile and drilbur be excadrill sooner rather than later.

Yes some will learn their attacks sooner, but mostly this makes it more challenging and enjoyable for me to go through the story with some of my favorites